Ultra-high frequency antenna system



Nov. 20,. 1956 A. e. KANDOIAN 2,

ULTRA HIGH-"FREQUENCY ANTENNA SYSTEM Filed Feb. 11, 1953 2 Sheets-Sheet 1 INVENTOR ARM/6 6. KANDO/AN ATTO RN EY Nov. 20, 1956 A. e. KANDOIAN 2,

ULTRA-HIGH FREQUENCY ANTENNA SYSTEM Filed Feb. 11, 1953 2 Sheets-Sheet 2 I E l l I E l INVENTOR I ARM/6 6. KANDO/AN ATTORNEY United States Patent 2,771,606 ULTRA-HIGH FREQUENCY ANTENNA SYSTEM Armig G. Kandoian, Glen Rock, N. J., assignor to International Telephone and Telegraph Corporation, a corporation of Maryland Application February 11, 1953, Serial No. 336,396 1 Claim. (Cl. 343-890) This invention relates to an ultra-high frequency antenna system and more particularly to a rigid structural support for an antenna array having a plurality of loop radiators for use as a high gain transmitting antenna for an ultra frequency television station.

In high frequency transmission systems such as are used for frequency modulation or television transmissions, it is desirable that the radiation pattern of the transmitting antenna array be directed in a horizontal direction from an antenna structure which is elevated above ground, in order that the transmitted signal level be high at points distant from the transmitter. In order to provide such a desired signal level at distant points it is essential to provide an array of antenna units for concentrating the emitted energy. Since such an antenna array must be supported in a position elevated above ground, it is essential for practical reasons that the individual radiators be relatively small and that the supporting structure not interfere with the radiated pattern.

In the past horizontally polarized loop antennas have been found to be the most satisfactory radiator units. In such antennas the diameter of the loop radiator is dependent upon the frequency of transmission, thus the higher the transmitted frequency the smaller the diameter of the loop radiator. Previously when transmission of television or frequency modulation signals occurred in the lower frequency spectrum the diameter of the loop radiators used, were sufficiently large to encompass a supporting structure of sulficient cross-sectional area to provide the required rigidity. However, as the frequency of transmission was raised to the ultrahigh frequency spectrum it was found that the diameter of the loop radiator became far too small to encompass a self-supporting rigid antenna structure. At low frequencies it was found impractical to stack the required number of radiators to obtain a high gain antenna system but at higher frequencies it is quite practical to stack a greater number of loop radiators to get a high antenna gain. Since a high antenna gain is used with a high frequency transmission system rigidity of the support structure is essential.

When the loop radiators were located inside the supporting structure it was found that the antenna pattern was disturbed due to the interference of the structure. Attempts have been made to provide a self-supporting rigid antenna structure for ultra-high frequency loop radiators which would not interfere with the radiation pattern of the antenna array, but these attempts heretofore have not met with success.

Furthermore, it was also found desirable that an antenna system for use with television signal emissions be capable of being weatherproofed or pressurized in order to reduce the cost of maintenance to a minimum and be capable of having each of its individual radiators fed in phase in order to maintain the desired transmission pattern.

One of the objects of this invention, therefore, is to 2,771,606 Patented Nov. 20, 1956 provide a rigid self-supporting high gain antenna array structure with a plurality of ultra-high frequency loop radiators disposed inside the structural lattice thereof.

Another object of this invention is to provide a high gain antenna array in which ultra-high frequency horizontal polarized loop antennas are located inside a rigid self-supporting lattice structure which does not interfere with the radiated pattern.

A feature of this invention is the use of a self-supporting antenna structure having vertical members encompassing a plurality of vertically stacked horizontally poralized loop radiators. Each of the loop radiators has a plurality of folded dipole radiating elements which are fed in phase by substantially equal lengths of transmission lines from an impedance matching transformer located at a central point. The vertical members are rigidly coupled together by a plurality of horizontal braces located between the loop radiators. Support frames associated with each of the loop radiators are connected to the vertical members and rigidly maintain the radiators in the center of the structure in such a manner that only vertical supports are disposed near each radiator allowing the antenna array system to radiate horizontally polarized emissions without interference from the supporting structure.

The above-mentioned and other features and objects of this invention will become more apparent by reference to the following description taken in conjunction with the accompanying drawings, in which:

Fig. l is a schematic illustration in elevation of one antenna system in accordance with the principles of this invention;

Fig. 2 is a cross-sectional view taken along the lines 22 of Fig. 1;

Fig. 3 is a view in perspective of one form of horizontally polarized loop radiator for use with the antenna system shown in Fig. 1;

Fig. 4 is a schematic illustration in elevation of an alternate embodiment in an antenna system in accordance with the principles of this invention, and;

Fig. 5 is a cross-sectional view taken along lines of 55 of Fig. 4.

Referring to Figs. 1 and 2, antenna system in accordance with the principles of this invention is shown comprising a supporting structure 1 encompassing a plurality of vertically stacked horizontally polarized loop radiators 2. The support structure 1 comprises three vertical tubular members 3, 4, and 5, each composed of a material having a high structural strength, such as steel, located at the vertices of an equilateral triangle. Connecting the vertical members 3, 4, and 5 are a plurality of horizontal brace members 6. The support structure which may be divided into a plurality of substantially identical sections, such as an upper section '7 and a lower section 8, by a junction box 9 which may contain an impedance matching transformer and extra lengths of cable. The vertical members 3, 4, and 5 may be located in an elevated position by being placed on a tower base It]; or if desired the vertical supports may be located on the ground. Each of the loop radiators 2 is located inside the area encompassed by the vertical members 3, 4, and 5 and between horizontal brace members 6. Thus the supporting structure disposed horizontally of each loop radiator 2 contains only vertical members eliminating any possibility of the antenna structure interfering with the radiation pattern from the stack of horizontally polarized loop radiators. Additional diagonal braces 6A may be utilized in the structure disposed horizontally of junction box 9.

Referring to Fig. 3 one embodiment of a horizontally polarized loop radiator for use with the antenna structure shown in Fig. 1 comprises a triangular loop radiator having three half folded dipole antenna units 11, 12, and 13. Each half folded dipole antenna unit comprises a pair of rectangular metallic elements 14 and 15 having their inner edges separated by space 16. An impedance matching device 17 is coupled to the outer edge of element 14 and the inner edge of element 15. The units 11, 12, and 13 are joined to a common feed point 18 by means of radial support members 19. The inner conductor 2% of a transmission feed line 21 is divided at point 18 and coupled to the inner edge of elements 14. The return path includes the support structure 1 which acts as the equivalent of an outer conductor for the feed line. Each loop radiator 2 is coupled to the vertical support members 3, 4, and 5 by means of a tubular hub-like member 22 connected to radial members 19 and to which spokes 23 are connected coupling the tubular member 22 to the vertical supports 3, 4, and 5 by means of clamps 24. The spokes 23 are located between horizontal braces 6 in such a manner as to keep 1 the zone immediately surrounding each loop radiator 2 free of horizontal or diagonal structure members thereby insuring that the radiations emitted by the antenna array will be free of interference from the support structure. to the horizontal members 6, the hub mounting for the loop radiator being such as to locate the radiators in the zone defined by the vertical members and the adjacent horizontal members.

One form of antenna design which I have found satisfactory comprises a vertical stack of horizontal loop radiators which are fed in parallel in groups of twelve. The optimum supporting structure was found to be a steel lattice 20 inches on a side. provided in order to be able to vertically stack loop radiators to a maximum aperture of approximately fifty feet while still maintaining a rigid structure. The radiating loops were located inside the steel lattice at a vertical spacing of approximately one wave length. The

vertical tubular members were approximately 1 /2 inches in diameter and the horizontal braces approximately 4 inches wide. Such an antenna system will withstand winds of extremely high velocity without additional braces; i. e., an antenna structure 50 feet in height will be able to withstand winds of approximately 100 miles per hour without a deflection of more than 3 to 4 inches.

Referring to Figs. 4 and 5 an alternate embodiment of an antenna system in accordance with the principles of this invention is shown wherein the antenna support structure 25 comprises four vertical support members If desired, the spokes 23 may be clamped This size lattice was 26, 27, 28, and 29, each located at the corner of a square. Horizontal braces 30 rigidly connect the vertical support members. In a manner similar to the antenna system shown in Fig. 1, loop radiators 31 are located between alternate horizontal braces 30 and substantially one wave length apart. To insure additional strength diagonal structural members 32 may be added between alternate braces 30. The use of four vertical support members provides a greater cross-sectional area and thus allows the use of a horizontally polarized loop radiator having a greater diameter than the loop radiator shown in Fig. 3. Any well-known loop radiator capable of transmitting in the ultra-high frequency band may be used in combination with the supporting structure of this invention. By locating the radiators inside the supporting structure, each radiator may be surrounded with a sealing compound and thus be pressurized against weather. Alternately the entire structure may be enclosed in a radome.

While I have described above the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of any invention as set forth in the objects thereof and the accompanying claim.

I claim: v

An antenna array comprising a support structure including a plurality of vertical support members disposed about a central vertical axis to form a substantially closed geometric pattern having a given horizontal crosssectional area and horizontal brace members interconnecting said vertical support members in vertically spaced planes to form a sturdy tower construction, a plurality of horizontally polarized loop radiators of loop area smaller than said cross-sectional area, each of said loop radiators having an axially disposed hub and a plurality of spoke supports disposed radially thereof and means coupling said spoke supports to said support structure to locate the radiator within the zone defined by said vertical support members and two adjacent planes formed by horizontal brace members.

References Cited in the file of this patent UNITED STATES PATENTS 2,238,904 Lindenblad Apr. 22, 1941 2,310,853 'Lindenblad Feb. 9, 1943 2,533,236 Felsenheld Dec. 12, 1950 FOREIGN PATENTS 598,548 Great Britain Feb. 20, 1948 

